[Bug rtl-optimization/115565] [11/12/13/14/15 Regression] CSE: Comparison incorrectly evaluated as constant causing optimization to produce wrong code

[roger at nextmovesoftware dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115565

Roger Sayle <roger at nextmovesoftware dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2024-06-20
             Status|UNCONFIRMED                 |NEW
                 CC|                            |roger at nextmovesoftware dot 
com
     Ever confirmed|0                           |1

--- Comment #3 from Roger Sayle <roger at nextmovesoftware dot com> ---
Doh!  I hadn't noticed (twenty years ago) that -1 was used to represent an
invalid quantity number in CSE's comparison_qty field.  There was no mention of
this in my post or patch. Using INT_MIN looks like a reasonable (good) fix. 
Presumably backends that constrain values in hard register zero (before reload)
are rare, which is why no-one has noticed/been affected by this.

Thanks for the fix, and my apologies for the inconvenience.